I never had PCs do any god-killing (with the semi-exception of those lame Avatar series FR modules) but there was one guy in my old group who was obsessed on playing out god-vs-god grudge match duels -- I swear for a couple years this was the only kind of "D&D" he wanted to play.
I like the idea of gods walking among men (Odin, among others, did it all the time) and that high level characters might eventually find themselves in direct opposition to one or more gods (or at least godlings -- among which I include demon lords, archdevils, Tiamat, etc.). In both of those cases I think it's approporiate that the gods have stats and, honestly, with the power-level of D&D I tend to play at (almost everybody in the world who isn't a PC is 0-level, 9th level+ is "high level," 12-14th level is about the maximum you're ever going to see, 18th level is legendary "once in a millenium" stuff) the gods as statted in the books (especially the Greater Gods) are so far above where the PCs are that the effect is pretty much the same as if they were declared unbeatable by fiat (Iuz, Lolth, Tiamat, and some other demigod-types are "beatable," but no PC in any of my games is ever going to stand a chance in combat against Odin, especially on his home turf (where, per D&Dg, gods get extra special abilities and double (or is it triple) hp)).
I like the idea of gods walking among men (Odin, among others, did it all the time) and that high level characters might eventually find themselves in direct opposition to one or more gods (or at least godlings -- among which I include demon lords, archdevils, Tiamat, etc.). In both of those cases I think it's approporiate that the gods have stats and, honestly, with the power-level of D&D I tend to play at (almost everybody in the world who isn't a PC is 0-level, 9th level+ is "high level," 12-14th level is about the maximum you're ever going to see, 18th level is legendary "once in a millenium" stuff) the gods as statted in the books (especially the Greater Gods) are so far above where the PCs are that the effect is pretty much the same as if they were declared unbeatable by fiat (Iuz, Lolth, Tiamat, and some other demigod-types are "beatable," but no PC in any of my games is ever going to stand a chance in combat against Odin, especially on his home turf (where, per D&Dg, gods get extra special abilities and double (or is it triple) hp)).